We pick h.root-servers.net, one of the 13 root servers (1), and ask it about webmail.alere.com and learn that com is delegated to 13 name servers (2), so we ask h.gtld-servers.net where we learn that alere.com is delegated to two name servers, including pdns1.cscdns.net (3), so we ask that one and get the following answer: